There are numerous optical processes for measuring the dimensions of objects and in particular the dimensions of the transverse cross-section of rolled sections by taking measurements of distances and in general of angles associated with these distances. These types of processes involve scanning the cross-section with a transmitting field under the action of at least one deflector actuated by a rotational or translational movement.
The Applicant has, for example, already proposed a process in which a beam of radiation is transmitted onto the section and part of the radiation reflected by the section is detected by means of a receiver. The transverse cross-section is scanned by means of a rotating deflector and the reflected beam is kept in the field of observation of the receiver by synchronising the orientation of the transmitter and receiver axes.
The results obtained by such processes have proved very satisfactory and thus not only the quality of the rolled product but also the quality of the rolling operation have been able to be checked and monitored.
There is, however, always an interest in increasing the speed and accuracy of these measurements, on the one hand for reasons of economy and on the other hand for reasons of monitoring efficiency. If fact, production rates are continuously increasing and in order to monitor the products during manufacture measurements must be taken increasingly quickly. Furthermore, when long products or articles are produced it is important to be able to repeat the measurements as frequently as possible along the products so as to locate better the transition between a correct dimension and a dimension outside the permitted tolerance.